Trefoil

A trefoil (from Latin trifolium 'three-leaved plant') is a graphic form composed of the outline of three overlapping rings, used in architecture, Pagan and Christian symbolism, among other areas.

A simple trefoil shape in itself can be symbolic of the Trinity,[1] while a trefoil combined with an equilateral triangle was also a moderately common symbol of the Christian Trinity during the late Middle Ages in some parts of Europe, similar to a barbed quatrefoil.

In architecture and archaeology, a 'trefoil' describes a layout or floor plan consisting of three apses in clover-leaf shape, as for example in the Megalithic temples of Malta.

It should not be confused with the figure named in French heraldry tiercefeuille ("threefoil"), which is a stylized flower with three petals, and differs from the heraldic trefoil in being not slipped.

While the green trefoil is considered by many to be the symbol of Ireland, the harp has much greater officially recognized status.